The invention concerns an in-hub motor.
In-hub motors, as found, for example, in Winchester mechanisms in data processing, have been developed to provide a particularly high degree of freedom with respect to radial and axial eccentricity. Among other things, this freedom is obtained by giving the aluminum vat, which forms the hub and in which the magnetic yokes and magnets are secured, its fine machining, i.e., grinding or stripping, on the finished motor.
In the case of motors with a large ratio of torque to volume, the magnetic yoke and the plate hub are constructed as one piece and consist of magnetizable steel, which must have a rustproof coating. This rustproof coating prevents any machining of the hub in the finished motor, thus requiring that the hub be manufactured with very high precision before installation.
It must be borne in mind that the eccentricity tolerance of the finished motor should be the result of the sum of the eccentricity tolerances of the constituent parts so that, for example, the ball bearings, the plate hub itself, and the joining accuracy required at the time of assembly must remain below 5 .mu..
The rustproof coating must lie within these tolerance limits. On the other hand, it is not possible to avoid such a rustproof coating by the use of stainless steel because this steel would not exhibit those magnetic properties that are particularly necessary in this type of motor.
Thus, the expenditure of time and money in the production of this type of motor is very high due to grinding, honing, or polishing. This production expenditure cannot be reduced even if large quantities of the motor are produced.
The objective, therefore, should be to reduce this production expenditure as much as possible.